In one class of solenoid actuated fluid valves, there is a desire to have three or more valve configurations that correspond to different flow conditions through the valve. For instance, in some fluid control valves there is a desire to have a first closed configuration, a small open configuration that allows some limited amount of fluid flow through the valve, and a large open condition that allows relatively unrestricted fluid flow through the valve. Such a valve might find potential application in controlling fluid flow to a hydraulically driven piston where there is a desire to control the movement rate or acceleration rate of the piston.
One potential application for a multi configuration control valve might be in hydraulically-actuated fuel injectors that utilize a hydraulically driven intensifier piston to pressurize fuel. In a typical fuel injector of this type, a solenoid actuated control valve has two positions: a closed position and an open position. Thus, hydraulically-actuated fuel injectors typically do not include an intermediate operating condition as they are either fully on or fully off. There might be a motivation to adopt a multi configuration control valve in a hydraulically-actuated fuel injector since engineers are constantly seeking new ways to control injection rate shaping in order to improve combustion efficiency and reduce undesirable noise and exhaust emissions. For instance, engineers have observed that undesirable emissions can sometimes be reduced by creating an injection rate shape that includes a small pilot injection followed by a relatively large main injection. Since there is a strong correlation between the movement rate of the intensifier piston and the injection rate trace from a hydraulically-actuated fuel injector, a multi configuration control valve might provide an additional avenue for controlling injection rate shaping.
The present invention is directed to multi configuration fluid valves and using the same to produce rate shaping in a fuel injector.